Rotary abrasive element



E. w. HALL 2ND., ETAL ROTARY ABRASIVE ELEMENT Filed April 25, 1958 Oct. 6, 1959 2,907,145

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United States Patent cc 2,907,145 I ROTARY ABRASIVE ELENIENT Elisha W. Hall 2nd, Scituate, and Dominick R.'Paone,

East Weymouth, Mass, assignors to F. L. & J. Codman Company, Rockland, Mass, a corporation of Massachusetts Application April 25, 1958, Serial No. 730,994

3 Claims. (Cl. 51-1935) This invention relates to an abrading wheel of the general type illsutrated by the patent to Hall 2,819,567,

the circumference of the wheel, but being capable of flexing more or less if pressed against the work.

A wheel of considerable length of face usually comprises a plurality of sections assembled end to end on a spindle, although each section is in a sense complete in itself and might be considered a wheel with very narrow face. It may be termed an element and that word will be used in the description.

In operation a rotary wheel moves across the work in planes parallel to the axis of rotation. It is desirable to have a certain relative movement axially independent of actual bodily movement of either work or wheel, and the object of the invention is to provide for this while preserving the balance of the wheel as a whole.

The invention will be well understood by reference to the following description taken .in connection with the accompanying drawings, wherein:

Fig. 1 is a view of a portion of a wheel element with parts sucessively broken away;

Fig. 2 is an exploded view showing the parts in side elevation;

Fig. 3 is an exploded view showing the parts in edge elevation;

Fig. 4 is a view of one of the strips utilized to make the fingers and shows it before trimming; and

Fig. 5 is a diagrammatic view showing, developed in a plane, the peripheral surface of a wheel formed by assembling side by side a number of sections like that shown in Figs. 1, 2 and 3.

The abrasive character of the strips is indicated by stippling, but the stippling is limited to small areas to avoid an inartistic effect. Also, since the disclosure is of an element involving two parts in themselves of identical form, there is appended to the reference numeral the letters n and 0, suggestive, respectively, of the words nig and off to facilitate the description, but the reference numeral is also referred to without mentioning the additional letter where it has a generic application in the context.

Referring now to the drawings. Each element seen in Fig. 1 comprises two parts set side by side which, as in the above mentioned patent, comprise a center in the form of a circular disc 20, desirably formed from fiber board or binders board. These words are not used in any technical sense except insofar as, like the word cardboard they suggest a relatively cheap and expendable material such as may be made from agglomerated fibers. The word board suggests a certain substantial thickness, although small in comparison with superficial area. The element has a central opening 22 to receive a shaft. At suitable intervals around the periphery of the board it is slotted and, as best seen in Fig. 3, the slots 24 are prefer- 2,907,145 l 'atented' Oct. 6, 19 5 9 2 ablybeing-arranged at a slight angle to the radial. In these slots are mounted upstanding fingers 26 in circumfer'entially spaced relation, the fingers comprising one, herein two, strips of flexible material coated with abrasive granules, inthe nature of emery cloth or sandpaper. Usually a woven cloth will be utilized. The strips 26, considered as awhole, are of substantially greater width than the thickness of the center 20, and their length is greater than their width.

The preceding paragraph would apply to the construction shown in Patent 2,819,5 67 above referred to Herein the strips 26 are shown as of trapezoidal form as seen in Fig; '4, the longer base of the trapezoid being outward. The inner ends are inserted in slits 24 and the projecting portions folded over the opposite end faces of the disc20 and secured by adhesive, giving the strip a generally channel form although it is not sharply creased and will flare toward the outer end. End plates 30-n and 30-0 of thin fiber are secured by adhesive to the end faces of the element to complete the same and cover the folded over portions at the inner ends of the strips. The outer ends of the strips are trimmed to circular contour after assembly. Fig. 4 represents the untrimmed blank which is cut away along the dotted lines after assembly. The projecting fingers are in a sense closely arranged but are nevertheless spaced and independent at their outer ends when not stressed against the work.

Also, as contrasted with the prior construction, the two discs 20-n and 20-0 receive strips not throughout their entire peripheries, but only for a portion thereof, herein through an arc of 180 in each case, although for convenience in manufacture, the slots 24 may extend around the complete circumference, but half of their number are not functional.

The two discs 20-n and 20-0 are assembled side by side, but with the groups of fingers offset, the groups of adjacent discs not substantially overlapping on each other and the two groups collectively extending through an entire circumference, that is, there are no breaks in the circumference nor any substantial duplication along any axial line. Particularly because of the trapezoidal form of the strips and their relatively wide outer edges, their side portions may extend past the plane between the two discs 20-n and 20-0 and extend partially into the space of the adjacent disc which is free of fingers. This will be clear from Fig. 3 if it is observed what would occur if the two discs were brought together in an axial direction.

When the element is rapidly revolving, first one group of fingers engages the work and then the other, but with an effect substantially like that of-a circumferentially continuous face. However, there is a certain axial component of pressure at the end of the fingers and, assuming the work to be completely stationary, the abrasive action rapidly alternates between axially spaced but contiguous areas, giving the desired effect of an axial or drawing movement in the operation as a whole.

An important feature of the invention is that the construction we have described is perfectly balanced, which is most importantin polishing and abrading work, particularly at the high speeds which are commonly utilized in practice.

In Fig. 5 there is illustrated diagrammatically a wheel of extended axial length formed of a number of elements as shown in Fig. 1, assembled side by side. They need not, and preferably would not, be permanently fastened I together, but would be secured on the spindle by means of metallic end plates in well known manner. It is necessary to illustrate the point to show only two of the elements so assembled, although more might be used. Conveniently the orientation of the two elements is the same, and therefore the checkered pattern formed by the exposed edges of the groups of fingers 26, considered as a collectidn, is a-regular oneco mparable to the black squares ofa checkerboard, the parts of the several discs to which no fingers are attached corresponding to the white squares.

We are aware that the invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and we therefore-desire the present embodiment :to he considered in all respects as illustrative and not restrictive, as is in fact, clear in several matters from the description itself. Reference is to be had to the appended claims to indicate those principles of the invention exemplified by the particular embodiment described and which we dwire to secure by each disc having secured thereto at intervals throughout aiportion of its periphery the inner ends of a pluralityof upstanding fingers in circumferentially spaced relation, .each finger comprising at least one, but not more than a few strips of flexible sheet material having a coating of abrasive granules adherent thereon, atleast the outer ends of said strips being of a width greater than the thickness of the disc and being disposed in planes angular to the central plane of the disc, the fingers in each disc extending through only a portion of its circumference, the groups of fingers on adjacent discs being circumferentially offset from and not substantially .overlapping each other and the groups on a set of discs extending collectively throughout the entire circumference.

2. An element as set forth in claim 1 wherein the strips are trapezoidal with their longer bases outward and their outward portions transversally bent to V form.

3. A rotary abrading or polishing wheel of generally cylindrical contour having at its periphery at intervals along its axial length circumferential groups of spaced but closely arranged upstanding fingers, the fingers comprising strips of flexible material having a coating of abrasive granules adherent thereon, the outer edges of said strips being disposed in planes angular to the axis of the wheel, each group of fingers extending over only a portion of the wheel circumference, the groups of fingers as a collection providing a checkered pattern of exposed edges. 1

References Cited in the file of this patent UNITED STATES PATENTS 2,819,567 Hall Jan. 14, 1958 amm- 

